Zumdahl Chemprin 6e Tb Ch11

CHAPTER 11

Electrochemistry

1. Ammonium metavanadate reacts with sulfur dioxide in acidic solution as follows (hydrogen ions and H2O omitted): xVO3

– + ySO2 xVO2+ + ySO42–

The ratio x : y is

A) 1 : 1B) 1 : 2C) 2 : 1D) 1 : 3E) 3 : 1Ans: C Chapter/Section: 11.1 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: half-reaction Keyword 4: Balancing Oxidation-Reduction Reactions Keyword 5: Half-Reaction Method

2. What is the oxidation state of Mn in MnO2?A) +2B) +4C) +9D) -1E) +3Ans: B Chapter/Section: 11.1 Difficulty: easy Keyword 1: general chemistry Keyword 2: chemical reactions Keyword 3: types of chemical reactions Keyword 4: oxidation-reduction reaction Keyword 5: assigning oxidation-number

3. How many electrons are transferred in the following reaction? 2Cr2O7

2- + 14H+ + 6Cl– 2Cr3+ + 3Cl2 + 7H2O

A) 2B) 4C) 6D) 8E) none of theseAns: C Chapter/Section: 11.1 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: half-reaction Keyword 4: Balancing Oxidation-Reduction Reactions Keyword 5: half-reaction method

4. How many electrons are transferred in the following reaction? SO3

2–(aq) + MnO4–(aq) SO4

2–(aq) + Mn2+(aq)

A) 6B) 2C) 10D) 4E) 3Ans: C Chapter/Section: 11.1 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: half-reaction Keyword 4: Balancing Oxidation-Reduction Reactions Keyword 5: half-reaction method

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219 Chapter 11: Electrochemistry

Use the following to answer question 5:

Refer to the galvanic cell below (the contents of each half-cell are written beneath each compartment).

The standard reduction potentials are as follows:MnO4

– + 8H+ + 5e– Mn2+ + 4H2O E = 1.51 V

Cr2O72– +14H+ + 6e– 2 Cr3+ +7H2O E = 1.33 V

5. What is the oxidation state of Cr in Cr2O72–?

A) +7B) +6C) +12D) –1E) –2Ans: B Chapter/Section: 11.1 Difficulty: easy Keyword 1: general chemistry Keyword 2: chemical reactions Keyword 3: types of chemical reactions Keyword 4: oxidation-reduction reaction Keyword 5: assigning oxidation-number

6. The following reaction occurs in basic solution: Ag+ + Cu Ag + Cu2+

When the equation is balanced, what is the sum of the coefficients?

A) 8B) 7C) 6D) 5E) 4Ans: C Chapter/Section: 11.1 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: half-reaction Keyword 4: Balancing Oxidation-Reduction Reactions Keyword 5: half-reaction method

7. When the equation for the following reaction in basic solution is balanced, what is the sum of the coefficients? MnO2 + HO2

– MnO4–

A) 11B) 31C) 14D) 9E) 18Ans: D Chapter/Section: 11.1 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: half-reaction Keyword 4: Balancing Oxidation-Reduction Reactions Keyword 5: half-reaction method


Chapter 11: Electrochemistry 220

8. When the equation for the following reaction in basic solution is balanced, what is the sum of the coefficients? MnO4

–(aq) + CN–(aq) MnO2(s) + CNO–(aq)

A) 13B) 8C) 10D) 20E) 11Ans: A Chapter/Section: 11.1 Difficulty: moderate Keyword 1: general chemistry Keyword 2: acids and bases Keyword 3: half-reaction Keyword 4: Balancing Oxidation-Reduction Reactions Keyword 5: half-reaction method

9. The reaction below occurs in basic solution. In the balanced equation, what is the sum of the coefficients? Zn + NO3

– Zn(OH)42– + NH3

A) 12B) 15C) 19D) 23E) 27Ans: D Chapter/Section: 11.1 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: half-reaction Keyword 4: Balancing Oxidation-Reduction Reactions Keyword 5: half-reaction method

10. A strip of copper is placed in a 1 M solution of copper nitrate, and a strip of silver is placed in a 1 M solution of silver nitrate. The two metal strips are connected to a voltmeter by wires, and a salt bridge connects the solutions. The following standard reduction potentials apply:Ag+(aq) + e– Ag(s) E° = +0.80 V

Cu2+(aq) + 2e– Cu(s) E° = +0.34 VWhen the voltmeter is removed and the two electrodes are connected by a wire, which of the following does not take place?

A) Electrons flow in the external circuit from the copper electrode to the silver electrode.B) The silver electrode increases in mass as the cell operates.C) There is a net general movement of silver ions through the salt bridge to the copper half-cell.D) Negative ions pass through the salt bridge from the silver half-cell to the copper half-cell.E) Some positive copper ions pass through the salt bridge from the copper half-cell to the silver half-cell.Ans: C Chapter/Section: 11.1,11.2 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: construction of voltaic cells

11. Which metal, Al or Ni, could reduce Zn2+ to Zn(s) if placed in a Zn2+(aq) solution?Zn2+ + 2e- Zn E° = -0.76 VAl3+ + 3e- Al E° = -1.66 VNi2+ + 2e- Ni E° = -0.23 V

A) AlB) NiC) Both Al and Ni would work.D) Neither Al nor Ni would work.E) This cannot be determined.Ans: A Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: standard cell emfs and standard electrode potentials Keyword 5: strength of oxidizing and reducing agents



12. Which of the following is the best reducing agent? Cl2 + 2e- 2Cl- E° = 1.36 V

Mg2+ + 2e- Mg E° = -2.37 V2H+ + 2e- H2 E° = 0.00 V

A) Cl2

B) H2

C) MgD) Mg2+

E) Cl-

Ans: C Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: standard cell emfs and standard electrode potentials Keyword 5: strength of oxidizing and reducing agents

13. The following two half-reactions take place in a galvanic cell. At standard conditions, what species are produced at each electrode?

Sn2+ + 2e– Sn E° = –0.14 VCu2+ + 2e– Cu E° = 0.34 V

A) Sn is produced at the anode, and Cu2+ is produced at the cathode.B) Sn is produced at the anode, and Cu is produced at the cathode.C) Sn is produced at the cathode, and Cu2+ is produced at the anode.D) Cu is produced at the cathode, and Sn2+ is produced at the anode.E) Cu is produced at the anode, and Sn2+ is produced at the cathode.Ans: D Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: construction of voltaic cells

14. Which of the following is the strongest oxidizing agent? MnO4

– + 4H+ + 3e– MnO2 + 2H2O E° = 1.68 VI2 + 2e– 2I– E° = 0.54 VZn2+ + 2e– Zn E° = -0.76 V

A) MnO4–

B) I2

C) Zn2+

D) ZnE) MnO2

Ans: A Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: standard cell emfs and standard electrode potentials Keyword 5: strength of oxidizing and reducing agents

Use the following to answer questions 15-17:

Reaction E° (volts)Na+ + e– Na –2.71Al3+ + 3e– Al –1.66Fe2+ + 2e– Fe –0.44Co2+ + 2e– Co –0.28Cu2+ + 2e– Cu +0.34Ag+ + e– Ag +0.80Cl2 + 2e– 2Cl– +1.36F2 + 2e– 2F– +2.87



15. Which of the following would be the best reducing agent?A) Cl2

B) F2

C) NaD) Na+

E) F–

Ans: C Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: standard cell emfs and standard electrode potentials Keyword 5: strength of oxidizing and reducing agents

16. Silver will spontaneously reduce which of the following?A) Fe2+

B) Co2+

C) Na+

D) Al3+

E) none of theseAns: E Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: standard cell emfs and standard electrode potentials Keyword 5: strength of oxidizing and reducing agents

17. Determine the standard potential, E°, of a cell that employs the reactionCo + Ag+ Co2+ +Ag

A) 1.08 VB) 1.88 VC) -1.08 VD) -0.52 VE) none of theseAns: A Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: standard cell emfs and standard electrode potentials Keyword 5: calculating cell emfs

18. The standard potential for the reaction Zn + 2Ag+ Zn2+ + 2Ag is 1.56 V. Given that the standard reduction potential for Ag+ + e– Ag is 0.80 V, determine the standard reduction potential for Zn2+ + 2e– Zn.A) -0.76 VB) 0.04 VC) 0.76 VD) -0.38 VE) none of theseAns: A Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: standard cell emfs and standard electrode potentials Keyword 5: calculating cell emfs


The following questions refer to a galvanic cell that utilizes the following reaction (unbalanced):

(AuCl4)–(aq) + Cu(s) Au(s) + Cl–(aq) + Cu2+(aq)



19. Given the following information, determine the standard cell potential.Species Standard Reduction Potential (V)Au3+(aq) 1.498Cu2+(aq) 0.339

A) 1.159 VB) 1.837 VC) 1.979 VD) 1.462 VE) 2.102 VAns: A Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: standard cell emfs and standard electrode potentials Keyword 5: calculating cell emfs

20. Determine the number of electrons transferred during the reaction (when balanced).A) 2B) 3C) 4D) 6E) 9Ans: D Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: half-reaction Keyword 4: Balancing Oxidation-Reduction Reactions Keyword 5: half-reaction method

21. Choose the correct statement(s) given the following information:

Fe3+(aq) + e– Fe2+(aq) E° = 0.77 VFe(CN)6

3– + e– Fe(CN)64– E° = 0.36 V

I. Fe2+(aq) is more likely to be oxidized than Fe2+ complexed to CN–.II. Fe3+(aq) is more likely to be reduced than Fe3+ complexed to CN–.III. Complexation of Fe ions with CN– has no effect on their tendencies to

become oxidized or reduced.

A) I onlyB) II onlyC) I and IID) III onlyE) None of these is true.Ans: B Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: standard cell emfs and standard electrode potentials Keyword 5: strength of oxidizing and reducing agents






– + 8H+ + 5e– Mn2+ + 4H2O E = 1.51 V

Cr2O72– +14H+ + 6e– 2 Cr3+ +7H2O E = 1.33 V

22. What is the value of E°cell?A) –0.18 VB) 2.84 VC) 0.18 VD) 1.79 VE) 2.29 VAns: C Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: standard cell emfs and standard electrode potentials Keyword 5: calculating cell emfs

23. In the balanced cell reaction, what is the stoichiometric coefficient for H+?A) 5B) 6C) 30D) 22E) 2Ans: D Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: half-reaction Keyword 4: Balancing Oxidation-Reduction Reactions Keyword 5: half-reaction method


Consider an electrochemical cell with a copper electrode immersed in 1.0 M Cu2+ and a silver electrode immersed in 1.0 M Ag+.

Cu2+ + 2e– Cu E° = 0.34 V Ag+ + e– Ag E° = 0.80 V



24. Calculate E° for this cell.A) 1.48 VB) 1.26 VC) 1.14 VD) 0.46 VE) none of theseAns: D Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: standard cell emfs and standard electrode potentials Keyword 5: calculating cell emfs

25. Which of the electrodes is the anode?A) the copper electrodeB) the silver electrodeAns: A Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: construction of voltaic cells


Consider the galvanic cell shown below (the contents of each half-cell are written beneath each compartment).

The standard reduction potentials are as follows: Cr3+ + 3e– Cr(s) E° = –0.73 V Br2(aq) + 2e– 2Br– E° = +1.09 V

26. What is E° for this cell?A) 1.82 VB) 0.36 VC) 4.75 VD) 1.79 VE) 4.40 VAns: A Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: standard cell emfs and standard electrode potentials Keyword 5: calculating cell emfs



27. Which of the following statements about this cell is false?A) This is a galvanic cell.B) Electrons flow from the Pt electrode to the Cr electrode.C) Reduction occurs at the Pt electrode.D) The cell is not at standard conditions.E) To complete the circuit, cations migrate into the left half-cell and anions migrate into the right half-

cell from the salt bridge.Ans: B Chapter/Section: 11.2 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: construction of voltaic cells


The reaction Cr(s) + NO3–(aq) Cr3+(aq) + NO(g) takes place in acidic solution.

28. How many electrons are transferred per mole of NO(g)?A) 1B) 2C) 3D) 4E) 5Ans: C Chapter/Section: 11.2 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: half-reaction Keyword 4: Balancing Oxidation-Reduction Reactions Keyword 5: half-reaction method

29. What is the coefficient of H2O(l) in the balanced equation?A) 1B) 2C) 3D) 4E) 5Ans: B Chapter/Section: 11.2 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: half-reaction Keyword 4: Balancing Oxidation-Reduction Reactions Keyword 5: half-reaction method




– + 8H+ + 5e– Mn2+ + 4H2O E = 1.51 V

Cr2O72– +14H+ + 6e– 2 Cr3+ +7H2O E = 1.33 V



30. When current is allowed to flow, which species is oxidized?A) Cr2O7

2–

B) Cr3+

C) MnO4–

D) Mn2+

E) H+

Ans: B Chapter/Section: 11.2,11.4 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: standard cell emfs and standard electrode potentials Keyword 5: strength of oxidizing and reducing agents

31. When current is allowed to flow, which species is reduced?A) Cr2O7

2–

B) Cr3+

C) MnO4–

D) Mn2+

E) H+

Ans: C Chapter/Section: 11.2,11.4 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: standard cell emfs and standard electrode potentials Keyword 5: strength of oxidizing and reducing agents

32. In which direction do electrons flow in the external circuit?A) left to rightB) right to leftC) No current flows; the cell is at equilibrium.Ans: B Chapter/Section: 11.2,11.4 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: construction of voltaic cells

33. How many electrons are transferred in the balanced reaction (that is, what will be the value of n in the Nernst equation)?A) 5B) 6C) 30D) 22E) 2Ans: C Chapter/Section: 11.2,11.4 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: half-reaction Keyword 4: Balancing Oxidation-Reduction Reactions Keyword 5: half-reaction method


In a common car battery, six identical cells each carry out the following reaction: Pb + PbO2 + 2HSO4

– + 2H+ 2PbSO4 + 2H2O

34. For such a cell, E° is 2.04 V. Calculate G° at 25°C.A) -787 kJB) -98 kJC) -394 kJD) -197 kJE) -0.121 kJAns: C Chapter/Section: 11.3 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: electromotive force



35. The reduction potentials for Au3+ and Ni2+ are as follows: Au3+ + 3e– Au E° = +1.50 V

Ni2+ + 2e– Ni E° = –0.23 V

Calculate G° (at 25°C) for the reaction

2Au3+ + 3Ni 3Ni2+ + 2Au

A) –5.00 102 kJB) +5.00 102 kJC) –2140 kJD) +1.00 103 kJE) –1.00 103 kJAns: E Chapter/Section: 11.3 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: electromotive force

36. Consider the following reduction potentials:Cu2+ + 2e– Cu E° = +0.34 VPb2+ + 2e– Pb E° = –0.13 VFor a galvanic cell employing the Cu, Cu2+ and Pb, Pb2+ couples, calculate the maximum amount of work that would accompany the reaction of 1 mol of lead under standard conditions.

A) –40.5 kJB) –45.3 kJC) –90.7 kJD) No work can be done. The system is at equilibrium.E) none of theseAns: C Chapter/Section: 11.3 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: electromotive force

37. The standard free energies of formation of several aqueous species arekJ/mol

H+(aq) 0H2O(l) –237

CH3OH(aq) –163HCOOH(aq) –351e– 0What is the standard reduction potential of methanoic acid in aqueous solution (that is, for HCOOH + 4H+ + 4e– CH3OH + H2O)?

A) +0.13 VB) +0.17 VC) +0.25 VD) –0.13 VE) –0.25 VAns: A Chapter/Section: 11.3 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: electromotive force



38. In which of the following cases can E° be equal to zero?I. In any cell at equilibriumII. In a concentration cellIII. E° can never be equal to zero.

A) I onlyB) II onlyC) IIID) I and IIAns: B Chapter/Section: 11.3,11.4 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration

39. In which of the following cases must E be equal to zero?I. In any cell at equilibriumII. In a concentration cellIII. E° can never be equal to zero.

A) I onlyB) II onlyC) IIID) I and IIAns: A Chapter/Section: 11.3,11.4 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration Keyword 5: Nernst equation

40. Consider the hydrogen–oxygen fuel cell where H2(g) + O2(g) H2O(l) G° = –237.18 kJ/mol H2

Which of the following statements is(are) true?

I. At standard conditions, the maximum work the fuel cell could do on the surroundings is 237.18 kJ/mol.II. In the real world, the actual amount of useful work the cell can do is less than 237.18 kJ.III. More energy is dissipated as waste heat in the fuel cell than in the reversible pathway.

A) IB) IIC) IIID) I, II, and IIIE) None of the statements is true.Ans: D Chapter/Section: 11.3,11.5 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: commercial voltaic cells



41. A fuel cell designed to react grain alcohol with oxygen has the following net reaction: C2H5OH(l) + 3O2(g) 2CO2(g) + 3H2O(l)

The maximum work that 1 mol of alcohol can yield by this process is 1320 kJ. What is the theoretical maximum voltage this cell can achieve?

A) 0.760 VB) 1.14 VC) 2.01 VD) 2.28 VE) 13.7 VAns: B Chapter/Section: 11.3,11.5 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: electromotive force

42. An excess of finely divided iron is stirred up with a solution that contains Cu2+ ion, and the system is allowed to come to equilibrium. The solid materials are then filtered off, and electrodes of solid copper and solid iron are inserted into the remaining solution. What potential develops between these two electrodes at 25°C?A) 0B) –0.78 VC) 0.592 VD) 0.296 VE) Not enough information is given.Ans: A Chapter/Section: 11.4 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: equilibrium constants from emfs


You make a cell with a copper electrode in a solution of copper nitrate and a silver electrode in a solution of silver nitrate.

Cu2+ + 2e– Cu E° = 0.34 V Ag+ + e– Ag E° = 0.80 V

43. If you could increase the concentration of Ag+, which of the following would be true about the cell potential?A) It would increase.B) It would decrease.C) It would remain constant.D) This cannot be determined.Ans: A Chapter/Section: 11.4 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration



44. If you could increase the concentration of Cu2+, which of the following would be true about the cell potential?A) It would increase.B) It would decrease.C) It would remain constant.D) This cannot be determined.Ans: B Chapter/Section: 11.4 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration

45. A cell is set up with copper and lead electrodes in contact with CuSO4(aq) and Pb(NO3)2(aq), respectively, at 25°C. The standard reduction potentials are Pb2+ + 2e– Pb E° = –0.13 V

Cu2+ + 2e– Cu E° = +0.34 V

If sulfuric acid is added to the Pb(NO3)2 solution, forming a precipitate of PbSO4, the cell potential

A) increases.B) decreases.C) is unchanged.D) It is impossible to tell what will happen.Ans: A Chapter/Section: 11.4 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration

46. A concentration cell is constructed using two Ni electrodes with Ni2+ concentrations of 1.64 M and 2.85 10–4 M in the two half-cells. The reduction potential of Ni2+ is –0.23 V. Calculate the potential of the cell at 25°C.A) +0.341 VB) –0.222 VC) –0.256 VD) +0.111 VE) –0.0078 VAns: D Chapter/Section: 11.4 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration Keyword 5: Nernst equation

47. The standard potential for the reaction A(s) + B3+(aq) A3+(aq) + B(s) is 0.50 V. What is the equilibrium constant K for this reaction at 25°C?A) 3.1 1025

B) 3.2 10–26

C) 17D) –17E) 0.015Ans: E Chapter/Section: 11.4 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: equilibrium constants from emfs



48. A concentration cell is constructed using two Co electrodes with Co2+ concentrations of 0.20 M and 4.4 10–5 M in the two half-cells. Determine the standard reduction potential of Co2+, given that the potential of the cell at 25°C is 0.108 V.A) 0 VB) +0.108 VC) –0.108 VD) +0.216 VE) This cannot be determined with the information given.Ans: E Chapter/Section: 11.4 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration Keyword 5: Nernst equation




Consider the galvanic cell shown below (the contents of each half-cell are written beneath each compartment).

The standard reduction potentials are as follows: Cr3+ + 3e– Cr(s) E° = –0.73 V Br2(aq) + 2e– 2Br– E° = +1.09 V

49. What is the value of E for this cell at 25°C?A) 2.21 VB) 1.76 VC) 2.12 VD) 1.88 VE) 0.59 VAns: D Chapter/Section: 11.4 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration Keyword 5: Nernst equation


Consider an electrochemical cell with a copper electrode immersed in 1.0 M Cu2+ and a silver electrode immersed in 1.0 M Ag+.

Cu2+ + 2e– Cu E° = 0.34 V Ag+ + e– Ag E° = 0.80 V

50. If [Cu2+]0 is 0.0034 M and [Ag+]0 is 0.34 M, calculate E.A) 0.52 VB) 0.59 VC) 0.51 VD) 0.41 VE) 0.40 VAns: C Chapter/Section: 11.4 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration Keyword 5: Nernst equation



51. For a reaction in a voltaic cell, both H° and S° are positive. Which of the following statements is true?A) E°cell will increase with an increase in temperature.B) E°cell will decrease with an increase in temperature.C) E°cell will not change when the temperature increases.D) G° > 0 for all temperatures.E) None of the above statements is true.Ans: A Chapter/Section: 11.4 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: electromotive force

52. Determine the equilibrium constant at 25°C for the reaction Zn + Ni2+ Zn2+ + Ni

Zn2+ + 2e– Zn E° = -0.76 V

Ni-2+ + 2e– Ni E° = -0.23 V

A) 8.6 1017

B) 9.3 108

C) 4.1 103

D) 6.4 10–6

E) none of theseAns: A Chapter/Section: 11.4 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: equilibrium constants from emfs

53. If a reducing agent X reacts with an oxidizing agent A2+ to give X2+ and A, and the equilibrium constant for the reaction is 1.0, then what is the E° value for the oxidation–reduction reaction at 25°C?A) 0.0 VB) –1.0 VC) 1.0 VD) 0.030 VE) 0.55 VAns: A Chapter/Section: 11.4 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells

54. A galvanic cell is constructed with copper electrodes and Cu2+ in each compartment. In one compartment, [Cu2+] = 2.2 10–3 M, and in the other compartment, [Cu2+] = 2.3 M. Calculate the potential for this cell at 25°C. The standard reduction potential for Cu2+ is +0.34 V.A) 0.43 VB) –0.43 VC) 0.089 VD) –0.089 VE) 0.77 VAns: C Chapter/Section: 11.4 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration Keyword 5: Nernst equation



55. An excess of finely divided iron is stirred up with a solution that contains Cu2+ ion, and the system is allowed to come to equilibrium. The solid materials are then filtered off, and electrodes of solid copper and solid iron are inserted into the remaining solution. What is the value of the ratio [Fe2+]/[Cu2+] at 25°C?A) 1B) 0C) 2.5 1026

D) 4.0 10–27

E) none of theseAns: C Chapter/Section: 11.4 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: equilibrium constants from emfs


Consider an electrochemical cell that has a nickel electrode immersed in 1.0 M Ni2+ and a platinum electrode immersed in 0.010 M Co2+.

Co2+ + 2e– Co E° = –0.28 VNi2+ + 2e– Ni E° = –0.23 V

56. Calculate E for this cell.A) 0.05 VB) 0.11 VC) 0.51 VD) 0.56 VE) none of theseAns: B Chapter/Section: 11.4 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration Keyword 5: Nernst equation

57. Calculate the concentration of Ni2+ if the cell is allowed to run to equilibrium at 25°C.A) 1.1 MB) 1.0 MC) 0.020 MD) 1.9 10–4 ME) none of theseAns: C Chapter/Section: 11.4 Difficulty: difficult Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration Keyword 5: Nernst equation






– + 8H+ + 5e– Mn2+ + 4H2O E = 1.51 V

Cr2O72– +14H+ + 6e– 2 Cr3+ +7H2O E = 1.33 V

58. What is the value of Q, the reaction quotient, for this cell reaction?A) 6.7 1040

B) 1.5 10–41

C) 1.5 10–4

D) 6.7 103

Ans: B Chapter/Section: 11.4 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration

59. What is the cell potential at 25°C as read on the digital voltmeter?A) 0.18 VB) 2.58 VC) 0.10 VD) 0.59 VE) 0.26 VAns: E Chapter/Section: 11.4 Difficulty: difficult Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration Keyword 5: Nernst equation

60. What is the value of the equilibrium constant at 25°C for the net spontaneous cell reaction?A) 7.3 10–11

B) 4.3 10–92

C) 91D) 1.1 103

E) 2.3 1091

Ans: E Chapter/Section: 11.4 Difficulty: difficult Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: equilibrium constants from emfs



61. Calculate E at 25°C for this cell, given the following data:

Ag+ + e– Ag(s) E° = 0.80 V

Ni2+ + 2e– Ni(s) E° = –0.23 V

Ksp for AgCl = 1.6 10–10

A) 0.83 VB) 0.54 VC) 1.01 VD) 2.98 VE) This cannot be determined from the data givenAns: B Chapter/Section: 11.4 Difficulty: difficult Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration Keyword 5: Nernst equation

62. Use the following data to calculate the Ksp value at 25°C for PbSO4(s).E°

PbO2 + 4H+ + SO42– + 2e– PbSO4(s) + 2H2O +1.69

PbO2 + 4H+ + 2e– Pb2+ + 2H2O +1.46

A) 2.57 10105

B) 3.89 10–105

C) 5.9 107

D) 1.7 10–8

E) None of these is within 5% of the correct answer.Ans: D Chapter/Section: 11.4 Difficulty: difficult Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration Keyword 5: Nernst equation



63. Calculate the solubility product of silver iodide at 25°C, given the following data:E° (V)

AgI(s) + e– Ag(s) + I– –0.15I2(s) + 2e– 2I– +0.54Ag+ + e– Ag(s) +0.80

A) 2.9 10–3

B) 1.9 10–4

C) 2.1 10–12

D) 8.4 10–17

E) 3.5 10–20

Ans: D Chapter/Section: 11.4 Difficulty: difficult Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration Keyword 5: Nernst equation

64. Why is aluminum protected from corrosion? (Note: The standard reduction potential for Al3+ is -1.66 V.)A) Aluminum forms a protective oxide coating.B) The oxidation of aluminum is not a favored process, as seen by the standard reduction potential for

Al3+.C) Oxygen and aluminum have no affinity for one another.D) At least two of these are correct.E) Aluminum is not protected from corrosion.Ans: A Chapter/Section: 11.6 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: corrosion

65. If a constant current of 5.5 amperes is passed through a cell containing Cr3+ for 2.5 hour, how many grams of Cr will plate out onto the cathode? (The atomic mass of Cr is 51.996 g/mol.)A) 27 gB) 0.15 gC) 8.9 gD) 80 gE) 1.3 gAns: C Chapter/Section: 11.7 Difficulty: easy Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: electrolytic cells Keyword 4: aqueous electrolysis Keyword 5: electroplating of metals


In a common car battery, six identical cells each carry out the following reaction: Pb + PbO2 + 2HSO4

– + 2H+ 2PbSO4 + 2H2O

66. Suppose that to start a car on a cold morning, 136 amperes is drawn for 16.0 seconds from such a cell. How many grams of Pb are consumed? (The atomic mass of Pb is 207.19 g/mol.)A) 9.35 gB) 2.34 gC) 4.67 gD) 0.00913 gE) 0.428 gAns: B Chapter/Section: 11.7 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells




An antique automobile bumper is to be chrome plated. The bumper, which is dipped into an acidic Cr 2O72–

solution, serves as a cathode of an electrolytic cell. The atomic mass of Cr is 51.996; 1 faraday = 96,485 coulombs.

67. If oxidation of H2O occurs at the anode, how many moles of oxygen gas will evolve for every 1.56 102 g of Cr(s) deposited?A) 4.50 molB) 3.00 molC) 2.00 molD) 4.00 molE) 1.50 molAns: A Chapter/Section: 11.7 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: electrolytic cells Keyword 4: aqueous electrolysis Keyword 5: electroplating of metals

68. If the current is 21.4 amperes, how long will it take to deposit 1.72 102 g of Cr(s) onto the bumper?A) 49.7 hB) 24.9 hC) 41.4 minD) 15.8 hE) 16.6 hAns: B Chapter/Section: 11.7 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: electrolytic cells Keyword 4: aqueous electrolysis Keyword 5: electroplating of metals

69. Copper is electroplated from an aqueous CuSO4 solution. A constant current of 5.10 amp is applied by an external power supply. How long will it take to deposit 4.08 102 g of Cu? The atomic mass of copper is 63.546 g/mol.A) 67.5 hB) 33.7 hC) 2.44 hD) 135.0 hE) 101.2 hAns: A Chapter/Section: 11.7 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: electrolytic cells Keyword 4: aqueous electrolysis Keyword 5: electroplating of metals

70. What quantity of charge is required to reduce 32.4 g of NiCl2 to nickel metal? (1 faraday = 96,485 coulombs)A) 2.41 104 CB) 4.82 104 CC) 1.07 105 CD) 7.24 104 CE) 9.65 104 CAns: B Chapter/Section: 11.7 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: electrolytic cells Keyword 4: aqueous electrolysis Keyword 5: electroplating of metals



71. Electrolysis of a molten salt with the formula MCl, using a current of 3.86 amp for 16.2 min, deposits 1.52 g of metal. Identify the metal. (1 faraday = 96,485 coulombs)A) LiB) NaC) KD) RbE) CaAns: C Chapter/Section: 11.7 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: electrolytic cells Keyword 4: electrolysis of molten salts

72. If an electrolysis plant operates its electrolytic cells at a total current of 1.0 106 amp, how long will it take to produce one metric ton (one million grams) of Mg(s) from seawater containing Mg2+? (1 faraday = 96,485 coulombs)A) 2.2 hB) 2.4 daysC) 55 minD) 3.7 hE) 1 yearAns: A Chapter/Section: 11.7 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: electrolytic cells Keyword 4: aqueous electrolysis

73. Nickel is electroplated from a NiSO4 solution. A constant current of 4.88 amp is applied by an external power supply. How long will it take to deposit 2.22 102 g of Ni? (The atomic mass of Ni is 58.69 g/mol.)A) 41.5 hB) 20.8 hC) 1.38 hD) 62.3 hE) 24.9 minAns: A Chapter/Section: 11.7 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: electrolytic cells Keyword 4: aqueous electrolysis Keyword 5: electroplating of metals

74. A solution of MnO42– is electrolytically reduced to Mn3+. A current of 9.10 amp is passed through the

solution for 16.6 minutes. What is the number of moles of Mn3+ produced in this process? (1 faraday = 96,486 coulombs)A) 0.0939 molB) 0.000522 molC) 0.0235 molD) 0.0313 molE) 0.0470 molAns: D Chapter/Section: 11.7 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: electrolytic cells Keyword 4: aqueous electrolysis Keyword 5: electroplating of metals

75. How many seconds would it take to deposit 21.40 g of Ag (atomic mass = 107.87) from a solution of AgNO3 using a current of 10.00 amp?A) 9649 sB) 4825 sC) 3828 sD) 1914 sE) none of theseAns: D Chapter/Section: 11.7 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: electrolytic cells Keyword 4: aqueous electrolysis



76. Gold (atomic mass = 197 g/mol) is plated from a solution of chlorauric acid, HAuCl4; it deposits on the cathode. Calculate the time it takes to deposit 0.70 g of gold, passing a current of 0.10 amperes. (1 faraday = 96,485 coulombs)A) 0.95 hB) 2.9 hC) 3.8 hD) 0.0019 daysE) 1.9 hAns: B Chapter/Section: 11.7 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: electrolytic cells Keyword 4: aqueous electrolysis Keyword 5: electroplating of metals

77. An electrolytic cell process involves plating Zr(s) from a solution containing Zr4+. If 5.80 amp is run through this mixture for 1.86 h, what mass of Zr is plated?A) 36.7 gB) 0.153 gC) 0.101 gD) 9.18 gE) none of theseAns: D Chapter/Section: 11.7 Difficulty: moderate Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: electrolytic cells Keyword 4: aqueous electrolysis

78. Gold is produced electrochemically from an aqueous solution of Au(CN)2– containing an excess of CN–.

Gold metal and oxygen gas are produced at the electrodes. How many moles of O2 will be produced during the production of 1.00 mol of gold?A) 0.25 molB) 0.50 molC) 1.00 molD) 3.56 molE) 4.00 molAns: A Chapter/Section: 11.7 Difficulty: difficult Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: electrolytic cells Keyword 4: aqueous electrolysis

79. Fe2+ + 2e– Fe(s) E° = -0.440 V2H+ + 2e– H2(g) E° = 0.000 V

In a galvanic cell, the iron compartment contains an iron electrode, and [Fe2+] = 1.00 10-3 M. The hydrogen compartment contains a platinum electrode (PH2 = 1.00 atm) and a weak acid HA at an initial concentration of 1.00 M. If the observed cell potential is 0.333 V at 25°C, calculate Ka for the weak acid HA at 25°C.

Ans: Ka = 2.43 10-7 Chapter/Section: 11.4 Difficulty: difficult Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration Keyword 5: Nernst equation



80. Ag+ + e– Ag(s) E° = 0.80 VCu2+ + 2e– Cu(s) E° = 0.34 V

In a galvanic cell, the silver compartment contains a silver electrode and excess AgCl(s) (Ksp = 1.6 10–10). The copper compartment contains a copper electrode, and [Cu2+] = 2.0 M.

A. Calculate the potential for this cell at 25°C.

B. Assuming 1.0 L of 2.0 M Cu2+ in the copper compartment, calculate how many moles of NH3 would have to be added to establish the cell potential at 0.52 V at 25°C (assume no volume change on addition of NH3).

Cu2+ + 4NH3 Cu(NH3)42+ Kf = 1.0 1013

Ans: A. 0.16 V; B. 8.6 mol of NH3 Chapter/Section: 11.4 Difficulty: difficult Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration Keyword 5: Nernst equation

81. Cu2+ + 2e– Cu(s) E° = 0.34 V

V2+ + 2e– V(s) E° = -1.20 V

In a galvanic cell, the copper compartment contains a copper electrode and [Cu2+] = 1.00 M. The vanadium compartment contains a vanadium electrode and V2+ at an unknown concentration. The compartment containing the vanadium (1.00 L of solution) was titrated with 0.0800 M H2EDTA2–, resulting in the reaction:

H2EDTA2– + V2+ VEDTA2– + 2H+

The potential of the cell was monitored to determine the stoichiometric point for the process, which occurred when 500.0 mL of H2EDTA2– solution was added. At the stoichiometric point, Ecell was 1.98 V. The solution was buffered at pH 10.00.

A. Calculate Ecell before titration was carried out.

B. Calculate the equilibrium constant K for the titration reaction.

C. Calculate Ecell at the halfway point of titration.

Ans: A. 1.58 V; B. 1.4; C. 1.59 V Chapter/Section: 11.4 Difficulty: difficult Keyword 1: general chemistry Keyword 2: electrochemistry Keyword 3: voltaic cells Keyword 4: dependence of emf on concentration Keyword 5: Nernst equation


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